1. Field of the Invention
The present invention relates to a fluxgate. More particularly, the present invention relates to a sensing apparatus having a high-efficiency fluxgate and a control method thereof capable of reducing power consumption by minimizing driving current.
2. Background of the Related Art
A fluxgate is a sensor detecting a terrestrial magnetism. The fluxgate uses a high permeability material such as permalloy as a magnetic substance core for a driving coil to apply an excited magnetic field thereto. The fluxgate also uses magnetic saturation and nonlinear magnetic characteristics of the core to measure a second harmonic component proportionate to an external magnetic field, thereby measuring the strength of the external magnetic field.
FIG. 1 is a circuit diagram of the configuration of a fluxgate module having a fluxgate to detect a signal corresponding to terrestrial magnetism. As shown in FIG. 1, the fluxgate includes a driving coil 40 for applying current to excite a magnetic substance core with current, a pulse generator 10 for generating pulses to be applied to the driving coil 40, amplifiers 30 and 31 for amplifying pulses to be applied to a first end a and a second end b, of the driving coil 40, and an inverter 20 for inverting the pulse applied to the second end b of the driving coil 40 to generate current.
Signals for turning the current amplifiers 30 and 31 on and off are due to a pulse P1 generated from the pulse generator 10. The pulse P1 from the pulse generator 10 is directly transmitted to the current amplifier 30, and is inverted through the inverter 20 to have a reversed phase when transmitted to the current amplifier 31.
Thus, pulse signals P2 and P3 applied to the first and second ends a and b, respectively, of the driving coil 40, which are respectively connected to the amplifiers 30 and 31, have opposite phases. When, at q1 of FIG. 1, the pulse signal P2 has a high level at the first end a and the pulse signal P3 has a low level at the second end b, current flows from a to b along the coil 40. On the other hand, when, at q2 of FIG. 2, the pulse signal P2 has a low level at the first end a, and the pulse signal P3 has a high level at the other end b, current flows from b to a along the coil 40. As a result, current is applied to the driving coil 40 in response to the pulse signals, thereby exciting the magnetic substance core on which the driving coil 40 is wound.
To drive the fluxgate, the pulse generator 10 is driven to apply a pulse train to the driving coil 40. Thus, when the fluxgate is driven with the driving coil 40 being driven by the generated pulse train, current flows constantly causing a high current consumption in a unit time interval.
MEMS (Micro-Electro Mechanical System) is a technology implementing mechanical and electrical parts using a semiconductor manufacturing process. A fluxgate may be minimized and integrated using MEMS technology. A fluxgate manufactured by a MEMS manufacturing process for a potable small-size terminal is generally used when there is a limited power source. Therefore, characteristic high current consumption of a fluxgate in a unit time interval can be a significant problem.
Meanwhile, the signal detected from the fluxgate goes through chopping, amplification and filtering to be input to an analog-to-digital (A/D) converter. In this case, if there are a plurality of the fluxgates, a plurality of circuits for the chopping, amplification and filtering are needed. Therefore, in the case of a fluxgate sensing apparatus to detect 2-axis magnetism, space occupied by circuits for signal processing is large. Thus, the fluxgate sensing apparatus is not compact.